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Large pieces of charcoal can't be transported great distances,
大块的木炭不可能移动很长的距离，
they can't be picked up and lofted in smoke plumes or carried around the world
它们不存在于烟云中，也无法被分带到世界各处，
so therefore if we can find charcoal at each KT boundary location
所以如果我们能够在每个第三纪界线层中都找到木炭，
we can be sure that burning occurred at each site.
那么就可以断定森林大火遍及了地球的每个地方。
In 2003, Claire Belcher scoured North America looking for charcoal.
在2003年，Claire Belcher走遍了北美洲寻找木炭。
She collected samples from eight KT boundary sites, from New Mexico in the south right up into western Canada.
她从8个分布有第三纪界线层的地点采集样本，从南部的新墨西哥一直到加拿大西部。
In the lab she searched the samples for traces of charcoal, which show up white under the microscope.
在实验室里，她在样本中探寻着木炭的痕迹，可是样本在显微镜下却呈现出白色。
She was amazed at what she discovered... there was almost none.
她对自己的发现颇为吃惊，木炭几乎不存在。
What we did find however was a lot of this non charred plant material.
我们发现的是许多不曾烧焦的植物材料。
This was really surprising because it means that to have this amount of non charred plant material in the KT boundary rocks,
这一结果出人意料，因为它说明第三纪界线层中有大量未曾烧焦的植被，
there's no way that there can have been a globally extensive wild fire
那么也就根本不可能有全球范围内的自然大火，
because it just simply wouldn't have left so much non charred material on the rock record.
因为它不可能把这么多的未烧焦物质留在岩石档案中。
